The identity and reactivity of the NO. adducts of phenoxyl radicals will be probed by laser flash photolysis, stopped flow UV-vis and Fourier Transform infrared (FTIR) spectroscopy. These NO. adducts are important intermediates leading to the ultimate deactivation of a wide variety of biological systems, including Photosystem II, ribonucleotide reductase and prostaglandin H synthase. The tyrosyl free radicals known to be active in these systems have been shown to react in an unknown fashion with nitric oxide. Stopped flow spectroscopy will allow the direct measurement of reaction rates of phenoxyl radicals with NO., while FTIR spectroscopy can resolve the identity of the longer lived species produced. The project will begin with simple, stable phenoxyl radicals in non-aqueous solvents, then move to more biologically relevant phenols (tyrosine and protein models) and conditions (aqueous solutions with micelles and vesicles).